Zoom lens system, interchangeable lens apparatus and camera system

ABSTRACT

A zoom lens system, in order from an object side to an image side, comprising a first lens unit having negative optical power, a second lens unit having positive optical power, a third lens unit having negative optical power, and a fourth lens unit having positive optical power, wherein the third lens unit moves along an optical axis in focusing from an infinity in-focus condition to a close-object in-focus condition, and the conditions: 0.5&lt;|f 3 /f W |&lt;2.0 and 0.005&lt;d 3 /f W &lt;0.070 (f 3 : a focal length of the third lens unit, d 3 : an optical axial thickness of the third lens unit, f W : a focal length of the entire system at a wide-angle limit) are satisfied; an interchangeable lens apparatus; and a camera system are provided.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based on application No. 2010-286700 filed in Japanon Dec. 22, 2010, the contents of which are hereby incorporated byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to zoom lens systems, interchangeable lensapparatuses, and camera systems. In particular, the present inventionrelates to: compact and lightweight zoom lens systems having, as well asexcellent optical performance, short overall length, and being able tobe held with small lens barrel; and interchangeable lens apparatuses,and camera systems, each employing the zoom lens system.

2. Description of the Background Art

In recent years, interchangeable-lens type digital camera systems (alsoreferred to simply as “camera systems”, hereinafter) have been spreadingrapidly. Such interchangeable-lens type digital camera systems realize:taking of high-sensitive and high-quality images; high-speed focusingand high-speed image processing after image taking; and easy replacementof an interchangeable lens apparatus in accordance with a desired scene.Meanwhile, an interchangeable lens apparatus having a zoom lens systemthat forms an optical image with variable magnification is popularbecause it allows free change of focal length without the necessity oflens replacement.

Zoom lens systems having excellent optical performance from a wide-anglelimit to a telephoto limit have been desired as zoom lens systems to beused in interchangeable lens apparatuses. Various kinds of zoom lenssystems each having a negative lens unit located closest to an objectside, and a multiple-unit construction have been proposed.

For example, International Patent Publication No. 2008-072466 disclosesa variable magnification optical system having a three-or-more unitconstruction of negative, positive and negative lens units. In theoptical system, the interval between the first lens unit and the secondlens unit decreases when the magnification varies from a wide-anglelimit to a telephoto limit. The first lens unit includes at least onenegative lens and at least one positive lens. The second lens unit iscomposed of one positive lens and one negative lens, and has at leastone aspheric surface. There is defined the condition setting forth adistance from the most object side lens surface to an image surface, adifference in refractive index of each lens and a difference in Abbenumber of each lens in the second lens unit, and a distance from themost image side lens surface to the image surface.

Japanese Laid-Open Patent Publication No. 2001-116992 discloses a zoomlens having a four unit construction of negative, positive, negative andpositive lens units. In the zoom lens, when the magnification variesfrom a wide-angle limit to a telephoto limit, the first lens unit moveswith locus of a convex to the image side, the second lens unit moves tothe object side so that the interval between the second lens unit andthe first lens unit decreases, the third lens unit moves to the objectside so that the interval between the third lens unit and the secondlens unit increases, and the fourth lens unit moves to the object sideso that the interval between the fourth lens unit and the third lensunit decreases. The third lens unit is composed of one negative lens,and the negative lens has an aspheric surface.

In each of the variable magnification optical system and the zoom lensdisclosed in the above-mentioned patent literatures, the construction ofthe lens unit contributing focusing makes it difficult to reduce theoverall length of lens system although optical performance is maintainedat a certain level. In particular, increase in size of a lens barrelholding such variable magnification optical system or zoom lens cannotbe prevented.

SUMMARY OF THE INVENTION

An object of the present invention is to provide: a compact andlightweight zoom lens system having, as well as excellent opticalperformance, short overall length, and being able to be held with smalllens barrel; and an interchangeable lens apparatus, and a camera system,each employing the zoom lens system.

The novel concepts disclosed herein were achieved in order to solve theforegoing problems in the conventional art, and herein is disclosed:

a zoom lens system, in order from an object side to an image side,comprising a first lens unit having negative optical power, a secondlens unit having positive optical power, a third lens unit havingnegative optical power, and a fourth lens unit having positive opticalpower, wherein

the third lens unit moves along an optical axis in focusing from aninfinity in-focus condition to a close-object in-focus condition, and

the following conditions (1) and (2) are satisfied:0.5<|f ₃ /f _(W)|<2.0  (1)0.005<d ₃ /f _(W)<0.070  (2)

where

f₃ is a focal length of the third lens unit,

d₃ is an optical axial thickness of the third lens unit, and

f_(W) is a focal length of the entire system at a wide-angle limit.

The novel concepts disclosed herein were achieved in order to solve theforegoing problems in the conventional art, and herein is disclosed:

an interchangeable lens apparatus comprising:

a zoom lens system; and

a lens mount section which is connectable to a camera body including animage sensor for receiving an optical image formed by the zoom lenssystem and converting the optical image into an electric image signal,wherein

the zoom lens system, in order from an object side to an image side,comprises a first lens unit having negative optical power, a second lensunit having positive optical power, a third lens unit having negativeoptical power, and a fourth lens unit having positive optical power,wherein

the third lens unit moves along an optical axis in focusing from aninfinity in-focus condition to a close-object in-focus condition, and

the following conditions (1) and (2) are satisfied:0.5<|f ₃ /f _(W)|<2.0  (1)0.005<d ₃ /f _(W)<0.070  (2)

where

f₃ is a focal length of the third lens unit,

d₃ is an optical axial thickness of the third lens unit, and

f_(W) is a focal length of the entire system at a wide-angle limit.

The novel concepts disclosed herein were achieved in order to solve theforegoing problems in the conventional art, and herein is disclosed:

a camera system comprising:

an interchangeable lens apparatus including a zoom lens system; and

a camera body which is detachably connected to the interchangeable lensapparatus via a camera mount section, and includes an image sensor forreceiving an optical image formed by the zoom lens system and convertingthe optical image into an electric image signal, wherein

the zoom lens system, in order from an object side to an image side,comprises a first lens unit having negative optical power, a second lensunit having positive optical power, a third lens unit having negativeoptical power, and a fourth lens unit having positive optical power,wherein

the third lens unit moves along an optical axis in focusing from aninfinity in-focus condition to a close-object in-focus condition, and

the following conditions (1) and (2) are satisfied:0.5<|f ₃ /f _(W)|<2.0  (1)0.005<d ₃ /f _(W)<0.070  (2)

where

f₃ is a focal length of the third lens unit,

d₃ is an optical axial thickness of the third lens unit, and

f_(W) is a focal length of the entire system at a wide-angle limit.

According to the present invention, it is possible to provide: a compactand lightweight zoom lens system having, as well as excellent opticalperformance, short overall length, and being able to be held with smalllens barrel; and an interchangeable lens apparatus, and a camera system,each employing the zoom lens system.

BRIEF DESCRIPTION OF THE DRAWINGS

This and other objects and features of this invention will become clearfrom the following description, taken in conjunction with the preferredembodiments with reference to the accompanied drawings in which:

FIG. 1 is a lens arrangement diagram showing an infinity in-focuscondition of a zoom lens system according to Embodiment 1 (Example 1);

FIG. 2 is a longitudinal aberration diagram of an infinity in-focuscondition of a zoom lens system according to Example 1;

FIG. 3 is a longitudinal aberration diagram of a close-object in-focuscondition of a zoom lens system according to Example 1;

FIG. 4 is a lateral aberration diagram of a zoom lens system accordingto Example 1 at a telephoto limit in a basic state where image blurcompensation is not performed and in an image blur compensation state;

FIG. 5 is a lens arrangement diagram showing an infinity in-focuscondition of a zoom lens system according to Embodiment 2 (Example 2);

FIG. 6 is a longitudinal aberration diagram of an infinity in-focuscondition of a zoom lens system according to Example 2;

FIG. 7 is a longitudinal aberration diagram of a close-object in-focuscondition of a zoom lens system according to Example 2;

FIG. 8 is a lateral aberration diagram of a zoom lens system accordingto Example 2 at a telephoto limit in a basic state where image blurcompensation is not performed and in an image blur compensation state;

FIG. 9 is a lens arrangement diagram showing an infinity in-focuscondition of a zoom lens system according to Embodiment 3 (Example 3);

FIG. 10 is a longitudinal aberration diagram of an infinity in-focuscondition of a zoom lens system according to Example 3;

FIG. 11 is a longitudinal aberration diagram of a close-object in-focuscondition of a zoom lens system according to Example 3;

FIG. 12 is a lateral aberration diagram of a zoom lens system accordingto Example 3 at a telephoto limit in a basic state where image blurcompensation is not performed and in an image blur compensation state;

FIG. 13 is a lens arrangement diagram showing an infinity in-focuscondition of a zoom lens system according to Embodiment 4 (Example 4);

FIG. 14 is a longitudinal aberration diagram of an infinity in-focuscondition of a zoom lens system according to Example 4;

FIG. 15 is a longitudinal aberration diagram of a close-object in-focuscondition of a zoom lens system according to Example 4;

FIG. 16 is a lateral aberration diagram of a zoom lens system accordingto Example 4 at a telephoto limit in a basic state where image blurcompensation is not performed and in an image blur compensation state;

FIG. 17 is a lens arrangement diagram showing an infinity in-focuscondition of a zoom lens system according to Embodiment 5 (Example 5);

FIG. 18 is a longitudinal aberration diagram of an infinity in-focuscondition of a zoom lens system according to Example 5;

FIG. 19 is a longitudinal aberration diagram of a close-object in-focuscondition of a zoom lens system according to Example 5;

FIG. 20 is a lateral aberration diagram of a zoom lens system accordingto Example 5 at a telephoto limit in a basic state where image blurcompensation is not performed and in an image blur compensation state;and

FIG. 21 is a schematic construction diagram of an interchangeable-lenstype digital camera system according to Embodiment 6.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(Embodiments 1 to 5)

FIGS. 1, 5, 9, 13, and 17 are lens arrangement diagrams of zoom lenssystems according to Embodiments 1 to 5, respectively. Each FIG. shows azoom lens system in an infinity in-focus condition.

In each FIG., part (a) shows a lens configuration at a wide-angle limit(in the minimum focal length condition: focal length f_(W)), part (b)shows a lens configuration at a middle position (in an intermediatefocal length condition: focal length f_(M)/=√(f_(W)*f_(T))), and part(c) shows a lens configuration at a telephoto limit (in the maximumfocal length condition: focal length f_(T)). Further, in each FIG., eachbent arrow located between part (a) and part (b) indicates a lineobtained by connecting the positions of each lens unit respectively at awide-angle limit, a middle position and a telephoto limit, in order fromthe top. In the part between the wide-angle limit and the middleposition, and the part between the middle position and the telephotolimit, the positions are connected simply with a straight line, andhence this line does not indicate actual motion of each lens unit.

Moreover, in each FIG., an arrow imparted to a lens unit indicatesfocusing from an infinity in-focus condition to a close-object in-focuscondition. That is, in FIGS. 1, 5, 9, 13, and 17, the arrow indicatesthe moving direction of a third lens unit G3, which is described later,in focusing from an infinity in-focus condition to a close-objectin-focus condition. In FIGS. 1, 5, 9, 13, and 17, since the symbols ofthe respective lens units are imparted to part (a), the arrow indicatingfocusing is placed beneath each symbol of each lens unit for theconvenience sake. However, the direction along which each lens unitmoves in focusing in each zooming condition will be described later indetail for each embodiment.

The zoom lens system according to each of Embodiments 1 to 5, in orderfrom the object side to the image side, comprises: a first lens unit G1having negative optical power; a second lens unit G2 having positiveoptical power; a third lens unit G3 having negative optical power; and afourth lens unit G4 having positive optical power. In the zoom lenssystem according to each embodiment, in zooming, the first lens unit G1,the second lens unit G2, and the third lens unit G3 individually move inthe direction along the optical axis so that the intervals between therespective lens units, i.e., the interval between the first lens unit G1and the second lens unit G2, the interval between the second lens unitG2 and the third lens unit G3, and the interval between the third lensunit G3 and the fourth lens unit G4 vary. In the zoom lens systemaccording to each embodiment, these lens units are arranged in a desiredoptical power configuration, thereby achieving size reduction of theentire lens system while maintaining high optical performance.

In FIGS. 1, 5, 9, 13, and 17, an asterisk “*” imparted to a particularsurface indicates that the surface is aspheric. In each FIG., symbol (+)or (−) imparted to the symbol of each lens unit corresponds to the signof the optical power of the lens unit. In each FIG., a straight linelocated on the most right-hand side indicates the position of an imagesurface S.

Further, as shown in FIGS. 1, 9, 13, and 17, an aperture diaphragm A isprovided between a fourth lens element L4 and a fifth lens element L5 inthe second lens unit G2. As shown in FIG. 5, an aperture diaphragm A isprovided between a third lens element L3 and a fourth lens element L4 inthe second lens unit G2.

As shown in FIG. 1, in the zoom lens system according to Embodiment 1,the first lens unit G1, in order from the object side to the image side,comprises: a negative meniscus first lens element L1 with the convexsurface facing the object side; a negative meniscus second lens elementL2 with the convex surface facing the image side; and a positivemeniscus third lens element L3 with the convex surface facing the objectside. Among these, the second lens element L2 has two aspheric surfaces.

In the zoom lens system according to Embodiment 1, the second lens unitG2, in order from the object side to the image side, comprises: abi-convex fourth lens element L4; a negative meniscus fifth lens elementL5 with the convex surface facing the object side; a bi-convex sixthlens element L6; and a bi-convex seventh lens element L7. Among these,the fifth lens element L5 and the sixth lens element L6 are cementedwith each other. The fourth lens element L4 has two aspheric surfaces.Further, an aperture diaphragm A is provided between the fourth lenselement L4 and the fifth lens element L5.

In the zoom lens system according to Embodiment 1, the third lens unitG3 comprises solely a bi-concave eighth lens element L8. The eighth lenselement L8 has two aspheric surfaces.

In the zoom lens system according to Embodiment 1, the fourth lens unitG4, in order from the object side to the image side, comprises: apositive meniscus ninth lens element L9 with the convex surface facingthe image side; and a bi-convex tenth lens element L10. Among these, theninth lens element L9 has two aspheric surfaces.

In the zoom lens system according to Embodiment 1, the seventh lenselement L7 as a component of the second lens unit G2 corresponds to animage blur compensating lens unit described later, which moves in adirection perpendicular to the optical axis in order to opticallycompensate image blur.

In the zoom lens system according to Embodiment 1, in zooming from awide-angle limit to a telephoto limit at the time of image taking, thefirst lens unit G1 moves with locus of a convex to the image side, thesecond lens unit G2 monotonically moves to the object side, the thirdlens unit G3 monotonically and slightly moves to the object side, andthe fourth lens unit G4 is fixed relative to the image surface S. Thatis, in zooming, the first lens unit G1, the second lens unit G2, and thethird lens unit G3 individually move along the optical axis such thatthe interval between the first lens unit G1 and the second lens unit G2decreases, the interval between the second lens unit G2 and the thirdlens unit G3 increases, and the interval between the third lens unit G3and the fourth lens unit G4 varies.

Further, in the zoom lens system according to Embodiment 1, in focusingfrom an infinity in-focus condition to a close-object in-focuscondition, the third lens unit G3 moves to the image side along theoptical axis in any zooming condition.

As shown in FIG. 5, in the zoom lens system according to Embodiment 2,the first lens unit G1, in order from the object side to the image side,comprises: a negative meniscus first lens element L1 with the convexsurface facing the object side; and a positive meniscus second lenselement L2 with the convex surface facing the object side. The firstlens element L1 and the second lens element L2 each have two asphericsurfaces.

In the zoom lens system according to Embodiment 2, the second lens unitG2, in order from the object side to the image side, comprises: abi-convex third lens element L3; a negative meniscus fourth lens elementL4 with the convex surface facing the object side; a bi-convex fifthlens element L5; and a bi-concave sixth lens element L6. Among these,the fourth lens element L4 and the fifth lens element L5 are cementedwith each other. The third lens element L3 and the sixth lens element L6each have two aspheric surfaces. Further, an aperture diaphragm A isprovided between the third lens element L3 and the fourth lens elementL4.

In the zoom lens system according to Embodiment 2, the third lens unitG3 comprises solely a bi-concave seventh lens element L7. The seventhlens element L7 has two aspheric surfaces.

In the zoom lens system according to Embodiment 2, the fourth lens unitG4 comprises solely a bi-convex eighth lens element L8. The eighth lenselement L8 has two aspheric surfaces.

In the zoom lens system according to Embodiment 2, the sixth lenselement L6 as a component of the second lens unit G2 corresponds to animage blur compensating lens unit described later, which moves in adirection perpendicular to the optical axis in order to opticallycompensate image blur.

In the zoom lens system according to Embodiment 2, in zooming from awide-angle limit to a telephoto limit at the time of image taking, thefirst lens unit G1 moves with locus of a convex to the image side, thesecond lens unit G2 monotonically moves to the object side, the thirdlens unit G3 monotonically and slightly moves to the object side, andthe fourth lens unit G4 is fixed relative to the image surface S. Thatis, in zooming, the first lens unit G1, the second lens unit G2, and thethird lens unit G3 individually move along the optical axis such thatthe interval between the first lens unit G1 and the second lens unit G2decreases, the interval between the second lens unit G2 and the thirdlens unit G3 increases, and the interval between the third lens unit G3and the fourth lens unit G4 varies.

Further, in the zoom lens system according to Embodiment 2, in focusingfrom an infinity in-focus condition to a close-object in-focuscondition, the third lens unit G3 moves to the image side along theoptical axis in any zooming condition.

As shown in FIG. 9, in the zoom lens system according to Embodiment 3,the first lens unit G1, in order from the object side to the image side,comprises: a negative meniscus first lens element L1 with the convexsurface facing the object side; a negative meniscus second lens elementL2 with the convex surface facing the image side; and a positivemeniscus third lens element L3 with the convex surface facing the objectside. Among these, the first lens element L1 has an aspheric image sidesurface and the second lens element L2 has two aspheric surfaces.

In the zoom lens system according to Embodiment 3, the second lens unitG2, in order from the object side to the image side, comprises: abi-convex fourth lens element L4; a negative meniscus fifth lens elementL5 with the convex surface facing the object side; a bi-convex sixthlens element L6, and a bi-convex seventh lens element L7. Among these,the fifth lens element L5 and the sixth lens element L6 are cementedwith each other. The fourth lens element L4 has two aspheric surfaces.Further, an aperture diaphragm A is provided between the fourth lenselement L4 and the fifth lens element L5.

In the zoom lens system according to Embodiment 3, the third lens unitG3 comprises solely a negative meniscus eighth lens element L8 with theconvex surface facing the object side. The eighth lens element L8 hastwo aspheric surfaces.

In the zoom lens system according to Embodiment 3, the fourth lens unitG4 comprises solely a bi-convex ninth lens element L9. The ninth lenselement L9 has two aspheric surfaces.

In the zoom lens system according to Embodiment 3, the seventh lenselement L7 as a component of the second lens unit G2 corresponds to animage blur compensating lens unit described later, which moves in adirection perpendicular to the optical axis in order to opticallycompensate image blur.

In the zoom lens system according to Embodiment 3, in zooming from awide-angle limit to a telephoto limit at the time of image taking, thefirst lens unit G1 moves with locus of a convex to the image side, thesecond lens unit G2 monotonically moves to the object side, the thirdlens unit G3 monotonically and slightly moves to the object side, andthe fourth lens unit G4 is fixed relative to the image surface S. Thatis, in zooming, the first lens unit G1, the second lens unit G2, and thethird lens unit G3 individually move along the optical axis such thatthe interval between the first lens unit G1 and the second lens unit G2decreases, the interval between the second lens unit G2 and the thirdlens unit G3 increases, and the interval between the third lens unit G3and the fourth lens unit G4 varies.

Further, in the zoom lens system according to Embodiment 3, in focusingfrom an infinity in-focus condition to a close-object in-focuscondition, the third lens unit G3 moves to the image side along theoptical axis in any zooming condition.

As shown in FIG. 13, in the zoom lens system according to Embodiment 4,the first lens unit G1, in order from the object side to the image side,comprises: a negative meniscus first lens element L1 with the convexsurface facing the object side; a negative meniscus second lens elementL2 with the convex surface facing the image side; and a positivemeniscus third lens element L3 with the convex surface facing the objectside. Among these, the second lens element L2 has two aspheric surfaces.

In the zoom lens system according to Embodiment 4, the second lens unitG2, in order from the object side to the image side, comprises: abi-convex fourth lens element L4; a negative meniscus fifth lens elementL5 with the convex surface facing the object side; a bi-convex sixthlens element L6, and a bi-convex seventh lens element L7. Among these,the fifth lens element L5 and the sixth lens element L6 are cementedwith each other. The fourth lens element L4 has two aspheric surfaces.Further, an aperture diaphragm A is provided between the fourth lenselement L4 and the fifth lens element L5.

In the zoom lens system according to Embodiment 4, the third lens unitG3 comprises solely a negative meniscus eighth lens element L8 with theconvex surface facing the object side. The eighth lens element L8 hastwo aspheric surfaces.

In the zoom lens system according to Embodiment 4, the fourth lens unitG4, in order from the object side to the image side, comprises: apositive meniscus ninth lens element L9 with the convex surface facingthe image side; and a bi-convex tenth lens element L10. Among these, theninth lens element L9 has two aspheric surfaces.

In the zoom lens system according to Embodiment 4, the seventh lenselement L7 as a component of the second lens unit G2 corresponds to animage blur compensating lens unit described later, which moves in adirection perpendicular to the optical axis in order to opticallycompensate image blur.

In the zoom lens system according to Embodiment 4, in zooming from awide-angle limit to a telephoto limit at the time of image taking, thefirst lens unit G1 moves with locus of a convex to the image side, thesecond lens unit G2 monotonically moves to the object side, the thirdlens unit G3 monotonically and slightly moves to the object side, andthe fourth lens unit G4 is fixed relative to the image surface S. Thatis, in zooming, the first lens unit G1, the second lens unit G2, and thethird lens unit G3 individually move along the optical axis such thatthe interval between the first lens unit G1 and the second lens unit G2decreases, the interval between the second lens unit G2 and the thirdlens unit G3 increases, and the interval between the third lens unit G3and the fourth lens unit G4 varies.

Further, in the zoom lens system according to Embodiment 4, in focusingfrom an infinity in-focus condition to a close-object in-focuscondition, the third lens unit G3 moves to the image side along theoptical axis in any zooming condition.

As shown in FIG. 17, in the zoom lens system according to Embodiment 5,the first lens unit G1, in order from the object side to the image side,comprises: a negative meniscus first lens element L1 with the convexsurface facing the object side; a negative meniscus second lens elementL2 with the convex surface facing the image side; and a positivemeniscus third lens element L3 with the convex surface facing the objectside. Among these, the second lens element L2 has two aspheric surfaces.

In the zoom lens system according to Embodiment 5, the second lens unitG2, in order from the object side to the image side, comprises: abi-convex fourth lens element L4; a negative meniscus fifth lens elementL5 with the convex surface facing the object side; a bi-convex sixthlens element L6; and a bi-convex seventh lens element L7. Among these,the fifth lens element L5 and the sixth lens element L6 are cementedwith each other. The fourth lens element L4 has two aspheric surfaces.Further, an aperture diaphragm A is provided between the fourth lenselement L4 and the fifth lens element L5.

In the zoom lens system according to Embodiment 5, the third lens unitG3 comprises solely a bi-concave eighth lens element L8. The eighth lenselement L8 has two aspheric surfaces.

In the zoom lens system according to Embodiment 5, the fourth lens unitG4 comprises solely a bi-convex ninth lens element L9. The ninth lenselement L9 has two aspheric surfaces.

In the zoom lens system according to Embodiment 5, the seventh lenselement L7 as a component of the second lens unit G2 corresponds to animage blur compensating lens unit described later, which moves in adirection perpendicular to the optical axis in order to opticallycompensate image blur.

In the zoom lens system according to Embodiment 5, in zooming from awide-angle limit to a telephoto limit at the time of image taking, thefirst lens unit G1 moves with locus of a convex to the image side, thesecond lens unit G2 monotonically moves to the object side, the thirdlens unit G3 monotonically and slightly moves to the object side, andthe fourth lens unit G4 is fixed relative to the image surface S. Thatis, in zooming, the first lens unit G1, the second lens unit G2, and thethird lens unit G3 individually move along the optical axis such thatthe interval between the first lens unit G1 and the second lens unit G2decreases, the interval between the second lens unit G2 and the thirdlens unit G3 increases, and the interval between the third lens unit G3and the fourth lens unit G4 varies.

Further, in the zoom lens system according to Embodiment 5, in focusingfrom an infinity in-focus condition to a close-object in-focuscondition, the third lens unit G3 moves to the image side along theoptical axis in any zooming condition.

The zoom lens systems according to Embodiments 1 to 5 each have afour-unit construction of negative, positive, negative, and positivelens units, in which the third lens unit G3 is composed of one lenselement. Therefore, the thickness of the third lens unit G3 is small,thereby realizing a reduction in the overall length of lens system.Furthermore, in focusing from an infinity in-focus condition to aclose-object in-focus condition, the third lens unit G3 moves along theoptical axis, and the third lens unit G3 is sandwiched between the lensunits having positive optical power, i.e., the second lens unit G2 andthe fourth lens unit G4. Therefore, the negative optical power of thethird lens unit G3 itself can be easily increased. Accordingly, theamount of movement of the third lens unit G3 can be reduced in focusing,and thus the overall length of lens system is reduced, and moreover, theoverall length of lens system with the lens barrel being retracted isalso reduced.

In the zoom lens systems according to Embodiments 1 to 5, since thefourth lens unit G4 located closest to the image side is fixed relativeto the image surface in zooming from a wide-angle limit to a telephotolimit at the time of image taking, entry of dust or the like into thelens system is sufficiently prevented. Further, since the number of camcomponents is reduced, the configuration of the lens barrel can besimplified.

In the zoom lens systems according to Embodiments 1 to 5, since thefirst lens unit G1 located closest to the object side moves along theoptical axis in zooming from a wide-angle limit to a telephoto limit atthe time of image taking, the overall length of lens system is reduced,and moreover, the overall length of lens system with the lens barrelbeing retracted is also reduced.

The zoom lens systems according to Embodiments 1 to 5 are each providedwith an image blur compensating lens unit which moves in a directionperpendicular to the optical axis. The image blur compensating lens unitcompensates image point movement caused by vibration of the entiresystem, that is, optically compensates image blur caused by handblurring, vibration and the like.

When compensating image point movement caused by vibration of the entiresystem, the image blur compensating lens unit moves in the directionperpendicular to the optical axis, so that image blur is compensated ina state that size increase in the entire zoom lens system is suppressedto realize a compact construction and that excellent imagingcharacteristics such as small decentering coma aberration and smalldecentering astigmatism are satisfied.

The image blur compensating lens unit in the zoom lens system of thepresent invention may be a single lens unit. If a single lens unit iscomposed of a plurality of lens elements, the image blur compensatinglens unit may be any one lens element or a plurality of adjacent lenselements among the plurality of lens elements.

The following description is given for conditions preferred to besatisfied by a zoom lens system like the zoom lens systems according toEmbodiments 1 to 5. Here, a plurality of preferable conditions are setforth for the zoom lens system according to each embodiment. Aconstruction that satisfies all the plurality of conditions is mostdesirable for the zoom lens system. However, when an individualcondition is satisfied, a zoom lens system having the correspondingeffect is obtained.

For example, in a zoom lens system like the zoom lens systems accordingto Embodiments 1 to 5, which comprises, in order from the object side tothe image side, a first lens unit having negative optical power, asecond lens unit having positive optical power, a third lens unit havingnegative optical power, and a fourth lens unit having positive opticalpower, in which the third lens unit moves along an optical axis infocusing from an infinity in-focus condition to a close-object in-focuscondition (this lens configuration is referred to as a basicconfiguration of the embodiments, hereinafter), the following conditions(1) and (2) are satisfied.0.5<|f ₃ /f _(W)|<2.0  (1)0.005<d ₃ /f _(W)<0.070  (2)

where

f₃ is a focal length of the third lens unit,

d₃ is an optical axial thickness of the third lens unit, and

f_(W) is a focal length of the entire system at a wide-angle limit.

The condition (1) sets forth the relationship between the focal lengthof the third lens unit, and the focal length of the entire system at awide-angle limit. When the value goes below the lower limit of thecondition (1), the amount of generated aberrations at the time ofdecentering is increased. Conversely, when the value exceeds the upperlimit of the condition (1), the amount of movement of the third lensunit in focusing is increased, and the overall length of lens system isincreased.

When at least one of the following conditions (1)′ and (1)″ issatisfied, the above-mentioned effect is achieved more successfully.0.8<|f ₃ /f _(W)|  (1)′|f ₃ /f _(W)|<1.5  (1)″

The condition (2) sets forth the relationship between the thickness ofthe third lens unit, and the focal length of the entire system at awide-angle limit. When the value goes below the lower limit of thecondition (2), the thickness of a lens element as a component of thethird lens unit becomes excessively small, thereby it becomes difficultto process the lens element. Conversely, when the value exceeds theupper limit of the condition (2), it becomes difficult to ensure spaceson the object side and on the image side each relative to the third lensunit, thereby the overall length of lens system increases. Furthermore,the weight of the third lens unit contributing focusing increases, andthe size in an actuator becomes large.

When at least one of the following conditions (2)′ and (2)″ issatisfied, the above-mentioned effect is achieved more successfully.0.006<d ₃ /f _(W)  (2)′d ₃ /f _(W)<0.050  (2)″

For example, a zoom lens system having the basic configuration like thezoom lens systems according to Embodiments 1 to 5 preferably satisfiesthe following condition (3).0.30<d ₁ /f _(W)<0.85  (3)

where

d₁ is an optical axial thickness of the first lens unit, and

f_(W) is a focal length of the entire system at a wide-angle limit.

The condition (3) sets forth the relationship between the thickness ofthe first lens unit, and the focal length of the entire system at awide-angle limit. When the value goes below the lower limit of thecondition (3), the optical power of each lens element as a component ofthe first lens unit cannot be increased, which makes it difficult toreduce the overall length of lens system. Conversely, when the valueexceeds the upper limit of the condition (3), the overall length of lenssystem increases, and the overall length of lens system with the lensbarrel being retracted might increase.

When at least one of the following conditions (3)′ and (3)″ issatisfied, the above-mentioned effect is achieved more successfully.0.4<d ₁ /f _(W)  (3)′d ₁ /f _(W)<0.7  (3)″

The individual lens units constituting the zoom lens systems accordingto Embodiments 1 to 5 are each composed exclusively of refractive typelens elements that deflect incident light by refraction (that is, lenselements of a type in which deflection is achieved at the interfacebetween media having different refractive indices). However, the presentinvention is not limited to this construction. For example, the lensunits may employ diffractive type lens elements that deflect incidentlight by diffraction; refractive-diffractive hybrid type lens elementsthat deflect incident light by a combination of diffraction andrefraction; or gradient index type lens elements that deflect incidentlight by distribution of refractive index in the medium. In particular,in the refractive-diffractive hybrid type lens element, when adiffraction structure is formed in the interface between media havingdifferent refractive indices, wavelength dependence of the diffractionefficiency is improved. Thus, such a configuration is preferable.

(Embodiment 6)

FIG. 21 is a schematic construction diagram of an interchangeable-lenstype digital camera system according to Embodiment 6.

The interchangeable-lens type digital camera system 100 according toEmbodiment 6 includes a camera body 101, and an interchangeable lensapparatus 201 which is detachably connected to the camera body 101.

The camera body 101 includes: an image sensor 102 which receives anoptical image formed by a zoom lens system 202 of the interchangeablelens apparatus 201, and converts the optical image into an electricimage signal; a liquid crystal monitor 103 which displays the imagesignal obtained by the image sensor 102; and a camera mount section 104.On the other hand, the interchangeable lens apparatus 201 includes: azoom lens system 202 according to any of Embodiments 1 to 5; a lensbarrel 203 which holds the zoom lens system 202; and a lens mountsection 204 connected to the camera mount section 104 of the camera body101. The camera mount section 104 and the lens mount section 204 arephysically connected to each other. Moreover, the camera mount section104 and the lens mount section 204 function as interfaces which allowthe camera body 101 and the interchangeable lens apparatus 201 toexchange signals, by electrically connecting a controller (not shown) inthe camera body 101 and a controller (not shown) in the interchangeablelens apparatus 201. In FIG. 21, the zoom lens system according toEmbodiment 1 is employed as the zoom lens system 202.

In Embodiment 6, since the zoom lens system 202 according to any ofEmbodiments 1 to 5 is employed, a compact interchangeable lens apparatushaving excellent imaging performance can be realized at low cost.Moreover, size reduction and cost reduction of the entire camera system100 according to Embodiment 6 can be achieved. In the zoom lens systemsaccording to Embodiments 1 to 5, the entire zooming range need not beused. That is, in accordance with a desired zooming range, a range wheresatisfactory optical performance is obtained may exclusively be used.Then, the zoom lens system may be used as one having a lowermagnification than the zoom lens systems described in Embodiments 1 to5.

Numerical examples are described below in which the zoom lens systemsaccording to Embodiments 1 to 5 are implemented. Here, in the numericalexamples, the units of length are all “mm”, while the units of viewangle are all “°”. Moreover, in the numerical examples, r is the radiusof curvature, d is the axial distance, nd is the refractive index to thed-line, and vd is the Abbe number to the d-line. In the numericalexamples, the surfaces marked with * are aspherical surfaces, and theaspherical surface configuration is defined by the following expression.

$Z = {\frac{h^{2}/r}{1 + \sqrt{1 - {\left( {1 + \kappa} \right)\left( {h/r} \right)^{2}}}} + {\sum{A_{n}h^{n}}}}$Here, the symbols in the formula indicate the following quantities.

Z is a distance from a point on an aspherical surface at a height hrelative to the optical axis to a tangential plane at the vertex of theaspherical surface,

h is a height relative to the optical axis,

r is a radius of curvature at the top,

K is a conic constant, and

A_(n) is a n-th order aspherical coefficient.

FIGS. 2, 6, 10, 14, and 18 are longitudinal aberration diagrams of aninfinity in-focus condition of the zoom lens systems according toNumerical Examples 1 to 5, respectively.

FIGS. 3, 7, 11, 15, and 19 are longitudinal aberration diagrams of aclose-object in-focus condition of the zoom lens systems according toNumerical Examples 1 to 5, respectively. The object distance in each ofNumerical Examples 1 to 5 is 300 mm.

In each longitudinal aberration diagram, part (a) shows the aberrationat a wide-angle limit, part (b) shows the aberration at a middleposition, and part (c) shows the aberration at a telephoto limit. Eachlongitudinal aberration diagram, in order from the left-hand side, showsthe spherical aberration (SA (mm)), the astigmatism (AST (mm)) and thedistortion (DIS (%)). In each spherical aberration diagram, the verticalaxis indicates the F-number (in each FIG., indicated as F), and thesolid line, the short dash line and the long dash line indicate thecharacteristics to the d-line, the F-line and the C-line, respectively.In each astigmatism diagram, the vertical axis indicates the imageheight (in each FIG., indicated as H), and the solid line and the dashline indicate the characteristics to the sagittal plane (in each FIG.,indicated as “s”) and the meridional plane (in each FIG., indicated as“m”), respectively. In each distortion diagram, the vertical axisindicates the image height (in each FIG., indicated as H).

FIGS. 4, 8, 12, 16, and 20 are lateral aberration diagrams of the zoomlens systems at a telephoto limit according to Numerical Examples 1 to5, respectively.

In each lateral aberration diagram, the aberration diagrams in the upperthree parts correspond to a basic state where image blur compensation isnot performed at a telephoto limit, while the aberration diagrams in thelower three parts correspond to an image blur compensation state wherethe image blur compensating lens unit (Numerical Examples 1, and 3-5:the seventh lens element L7, Numerical Example 2: the sixth lens elementL6) is moved by a predetermined amount in a direction perpendicular tothe optical axis at a telephoto limit. Among the lateral aberrationdiagrams of a basic state, the upper part shows the lateral aberrationat an image point of 70% of the maximum image height, the middle partshows the lateral aberration at the axial image point, and the lowerpart shows the lateral aberration at an image point of −70% of themaximum image height. Among the lateral aberration diagrams of an imageblur compensation state, the upper part shows the lateral aberration atan image point of 70% of the maximum image height, the middle part showsthe lateral aberration at the axial image point, and the lower partshows the lateral aberration at an image point of −70% of the maximumimage height. In each lateral aberration diagram, the horizontal axisindicates the distance from the principal ray on the pupil surface, andthe solid line, the short dash line and the long dash line indicate thecharacteristics to the d-line, the F-line and the C-line, respectively.In each lateral aberration diagram, the meridional plane is adopted asthe plane containing the optical axis of the first lens unit G1 and theoptical axis of the second lens unit G2.

Here, in the zoom lens system according to each numerical example, theamount of movement of the image blur compensating lens unit in adirection perpendicular to the optical axis in an image blurcompensation state at a telephoto limit is as follows.

-   Numerical Example 1 0.256 mm-   Numerical Example 2 0.101 mm-   Numerical Example 3 0.192 mm-   Numerical Example 4 0.239 mm-   Numerical Example 5 0.329 mm

Here, when the shooting distance is infinity, at a telephoto limit, theamount of image decentering in a case that the zoom lens system inclinesby 0.3° is equal to the amount of image decentering in a case that theimage blur compensating lens unit displaces in parallel by each of theabove-mentioned values in a direction perpendicular to the optical axis.

As seen from the lateral aberration diagrams, satisfactory symmetry isobtained in the lateral aberration at the axial image point. Further,when the lateral aberration at the +70% image point and the lateralaberration at the −70% image point are compared with each other in thebasic state, all have a small degree of curvature and almost the sameinclination in the aberration curve. Thus, decentering coma aberrationand decentering astigmatism are small. This indicates that sufficientimaging performance is obtained even in the image blur compensationstate. Further, when the image blur compensation angle of a zoom lenssystem is the same, the amount of parallel translation required forimage blur compensation decreases with decreasing focal length of theentire zoom lens system. Thus, at arbitrary zoom positions, sufficientimage blur compensation can be performed for image blur compensationangles up to 0.3° without degrading the imaging characteristics.

Numerical Example 1

The zoom lens system of Numerical Example 1 corresponds to Embodiment 1shown in FIG. 1. Table 1 shows the surface data of the zoom lens systemof Numerical Example 1. Table 2 shows the aspherical data. Table 3 showsvarious data in an infinity in-focus condition. Table 4 shows variousdata in a close-object in-focus condition.

TABLE 1 (Surface data) Surface number r d nd vd Object surface ∞  116.51570 0.65000 1.91082 35.2  2 8.51100 5.25880  3* −16.68360 0.400001.58250 59.4  4* −1000.00000 0.20000  5 34.43510 1.29460 1.94595 18.0  6258.90520 Variable  7* 11.95340 2.23790 1.77200 50.0  8* −77.354301.00000  9(Diaphragm) ∞ 2.19170 10 79.81590 0.63640 1.80610 33.3 117.03480 2.78670 1.49700 81.6 12 −22.52390 1.20000 13 38.60240 1.208701.53172 48.8 14 −132.99270 Variable 15* −2019.57750 0.50000 1.85400 40.416* 13.35910 Variable 17* −35.48910 1.19570 1.54000 56.0 18* −32.187400.20000 19 27.45990 2.89460 1.74950 35.0 20 −1000.00000 (BF) Imagesurface ∞

TABLE 2 (Aspherical data) Surface No. 3 K = 0.00000E+00, A4 =1.14496E−04, A6 = −2.63339E−06, A8 = −1.86254E−07 A10 = 8.36834E−09, A12= −1.39484E−10, A14 = 8.35994E−13 Surface No. 4 K = 0.00000E+00, A4 =3.22844E−05, A6 = −1.61516E−06, A8 = −2.58608E−07 A10 = 1.09855E−08, A12= −1.82742E−10, A14 = 1.12056E−12 Surface No. 7 K = 0.00000E+00, A4 =−5.65218E−05, A6 = 2.07615E−06, A8 = −9.76031E−08 A10 = 1.35207E−09, A12= 0.00000E+00, A14 = 0.00000E+00 Surface No. 8 K = 0.00000E+00, A4 =4.73316E−05, A6 = 1.53465E−06, A8 = −8.63661E−08 A10 = 1.29651E−09, A12= 0.00000E+00, A14 = 0.00000E+00 Surface No. 15 K = 0.00000E+00, A4 =1.00000E−04, A6 = −3.79078E−07, A8 = −2.55568E−07 A10 = 7.54488E−09, A12= 0.00000E+00, A14 = 0.00000E+00 Surface No. 16 K = 0.00000E+00, A4 =1.18051E−04, A6 = 8.72304E−07, A8 = −3.47167E−07 A10 = 8.65929E−09, A12= 0.00000E+00, A14 = 0.00000E+00 Surface No. 17 K = 0.00000E+00, A4 =2.89636E−05, A6 = 3.33635E−06, A8 = −2.98315E−08 A10 = 1.60127E−10, A12= −1.19995E−11, A14 = 1.29100E−13 Surface No. 18 K = 0.00000E+00, A4 =−3.29778E−06, A6 = 3.33279E−06, A8 = −6.91825E−08 A10 = 1.49414E−09, A12= −2.58230E−11, A14 = 1.63269E−13

TABLE 3 (Various data in an infinity in-focus condition) Zooming ratio2.79706 Wide-angle Middle Telephoto limit position limit Focal length14.4900 24.2337 40.5294 F-number 3.64041 5.61725 5.82446 View angle41.0208 24.5065 14.8761 Image height 10.8150 10.8150 10.8150 Overalllength 63.0689 57.5243 59.9715 of lens system BF 14.19910 14.1988014.19808 d6 17.5987 6.8877 0.6000 d14 1.7513 6.2454 13.2385 d16 5.66476.3373 8.0798 Zoom lens unit data Lens Initial Focal unit surface No.length 1 1 −16.11373 2 7 13.78865 3 15 −15.53842 4 17 33.23596

TABLE 4 (Various data in a close-object in-focus condition) Wide-angleMiddle Telephoto limit position limit Object distance 300.0000 300.0000300.0000 BF 14.1990 14.1990 14.1990 d6 17.5987 6.8877 0.6000 d14 1.99046.9094 15.0277 d16 5.4255 5.6733 6.2906

Numerical Example 2

The zoom lens system of Numerical Example 2 corresponds to Embodiment 2shown in FIG. 5. Table 5 shows the surface data of the zoom lens systemof Numerical Example 2. Table 6 shows the aspherical data. Table 7 showsvarious data in an infinity in-focus condition. Table 8 shows variousdata in a close-object in-focus condition.

TABLE 5 (Surface data) Surface number r d nd vd Object surface ∞  1*1000.00000 0.90000 1.80139 45.4  2* 9.99800 3.64580  3* 17.16610 1.658602.01960 21.5  4* 29.11210 Variable  5* 16.42630 1.97770 1.69400 56.3  6*−37.20290 1.00990  7(Diaphragm) ∞ 3.09520  8 15.77370 0.40000 1.8061033.3  9 6.70050 3.08190 1.49700 81.6 10 −12.15640 0.50000 11* −51.849200.40000 1.54000 56.0 12* 13.41700 Variable 13* −45.67190 0.60000 1.8540040.4 14* 27.24990 Variable 15* 49.80370 3.64350 1.88202 37.2 16*−35.98030 (BF) Image surface ∞

TABLE 6 (Aspherical data) Surface No. 1 K = 0.00000E+00, A4 =1.99980E−05, A6 = −1.04256E−07, A8 = 0.00000E+00 A10 = 0.00000E+00Surface No. 2 K = 0.00000E+00, A4 = −6.96893E−05, A6 = 1.56825E−07, A8 =0.00000E+00 A10 = 0.00000E+00 Surface No. 3 K = 0.00000E+00, A4 =−1.27736E−04, A6 = 3.82918E−08, A8 = 3.40099E−09 A10 = 1.52940E−11Surface No. 4 K = 0.00000E+00, A4 = −1.27866E−04, A6 = −3.91493E−08, A8= 0.00000E+00 A10 = 0.00000E+00 Surface No. 5 K = 0.00000E+00, A4 =−1.22736E−04, A6 = 2.80029E−07, A8 = 0.00000E+00 A10 = 0.00000E+00Surface No. 6 K = 0.00000E+00, A4 = −1.87434E−05, A6 = 7.93029E−07, A8 =6.67886E−09 A10 = −1.06490E−10 Surface No. 11 K = 0.00000E+00, A4 =6.74583E−05, A6 = 2.66175E−06, A8 = 0.00000E+00 A10 = 0.00000E+00Surface No. 12 K = 0.00000E+00, A4 = 1.47632E−04, A6 = 2.24492E−06, A8 =−4.80293E−08 A10 = −3.38541E−09 Surface No. 13 K = 0.00000E+00, A4 =−1.23586E−05, A6 = −7.17560E−07, A8 = 0.00000E+00 A10 = 0.00000E+00Surface No. 14 K = 0.00000E+00, A4 = 5.15318E−06, A6 = −7.41915E−07, A8= 0.00000E+00 A10 = 0.00000E+00 Surface No. 15 K = 0.00000E+00, A4 =−2.58144E−05, A6 = 3.97612E−07, A8 = −1.98671E−09 A10 = 5.32957E−12Surface No. 16 K = 0.00000E+00, A4 = −2.41032E−05, A6 = 2.20393E−07, A8= 0.00000E+00 A10 = 0.00000E+00

TABLE 7 (Various data in an infinity in-focus condition) Zooming ratio2.79709 Wide-angle Middle Telephoto limit position limit Focal length14.4901 24.2339 40.5301 F-number 3.64074 5.30470 5.82455 View angle40.4927 24.1419 14.6372 Image height 10.8150 10.8150 10.8150 Overalllength 61.4480 56.7572 60.7683 of lens system BF 14.1990 14.1990 14.1990d4 18.9211 7.5672 0.7785 d12 2.7282 8.4782 17.7500 d14 4.6867 5.59927.1264 Zoom lens unit data Lens Initial Focal unit surface No. length 11 −20.83796 2 5 16.09236 3 13 −19.90929 4 15 24.16418

TABLE 8 (Various data in a close-object in-focus condition) Wide-angleMiddle Telephoto limit position limit Object distance 300.0000 300.0000300.0000 BF 14.1990 14.1990 14.1990 d4 18.9211 7.5672 0.7785 d12 3.21709.8505 21.6222 d14 4.1979 4.2269 3.2543

Numerical Example 3

The zoom lens system of Numerical Example 3 corresponds to Embodiment 3shown in FIG. 9. Table 9 shows the surface data of the zoom lens systemof Numerical Example 3. Table 10 shows the aspherical data. Table 11shows various data in an infinity in-focus condition. Table 12 showsvarious data in a close-object in-focus condition.

TABLE 9 (Surface data) Surface number r d nd vd Object surface ∞  116.40380 0.80000 1.85400 40.4  2* 8.70510 5.36700  3* −16.23400 0.500001.58700 59.6  4* −1000.00000 0.20000  5 22.10010 1.22670 1.94595 18.0  640.70380 Variable  7* 11.89400 2.01860 1.77200 50.0  8* −1000.000001.00000  9(Diaphragm) ∞ 2.00000 10 25.27820 0.60360 1.90366 31.3 117.33550 2.74960 1.49700 81.6 12 −33.30680 1.50000 13 33.70860 1.200001.58144 40.9 14 −92.62430 Variable 15* 89.01870 0.40000 1.77200 50.0 16*10.65000 Variable 17* 43.13480 3.20140 1.77200 50.0 18* −62.42310 (BF)Image surface ∞

TABLE 10 (Aspherical data) Surface No. 2 K = 0.00000E+00, A4 =−2.93817E−05, A6 = −3.76091E−07, A8 = 0.00000E+00 A10 = 0.00000E+00Surface No. 3 K = 0.00000E+00, A4 = 1.02745E−04, A6 = −2.96307E−06, A8 =7.20352E−08 A10 = −6.88162E−10 Surface No. 4 K = 0.00000E+00, A4 =8.27369E−05, A6 = −2.92460E−06, A8 = 6.16726E−08 A10 = −6.12881E−10Surface No. 7 K = 0.00000E+00, A4 = −4.56841E−05, A6 = 7.79393E−08, A8 =−5.36872E−09 A10 = −1.13968E−09 Surface No. 8 K = 0.00000E+00, A4 =4.14571E−05, A6 = −3.06241E−08, A8 = −1.38984E−08 A10 = −1.02011E−09Surface No. 15 K = 0.00000E+00, A4 = 1.00000E−04, A6 = −1.13790E−05, A8= 3.01367E−07 A10 = −3.11212E−09 Surface No. 16 K = 0.00000E+00, A4 =1.20867E−04, A6 = −1.18142E−05, A8 = 2.17820E−07 A10 = −1.42329E−09Surface No. 17 K = 0.00000E+00, A4 = 7.69393E−05, A6 = −9.88168E−07, A8= 1.17069E−08 A10 = −8.74673E−11 Surface No. 18 K = 0.00000E+00, A4 =5.55736E−05, A6 = −1.09755E−06, A8 = 1.39235E−08 A10 = −9.84665E−11

TABLE 11 (Various data in an infinity in-focus condition) Zooming ratio2.79711 Wide-angle Middle Telephoto limit position limit Focal length14.4902 24.2337 40.5305 F-number 3.64008 5.30432 5.82465 View angle40.7383 24.2803 14.8040 Image height 10.8150 10.8150 10.8150 Overalllength 62.5692 57.4360 60.2629 of lens system BF 14.1990 14.1990 14.1990d6 17.0276 6.6607 0.6000 d14 2.0929 6.5640 13.4281 d16 6.4825 7.24499.2689 Zoom lens unit data Lens Initial Focal unit surface No. length 11 −15.91283 2 7 13.59799 3 15 −15.70505 4 17 33.48446

TABLE 12 (Various data in a close-object in-focus condition) Wide-angleMiddle Telephoto limit position limit Object distance 300.0000 300.0000300.0000 BF 14.1990 14.1990 14.1990 d6 17.0276 6.6607 0.6000 d14 2.33417.2309 15.2027 d16 6.2412 6.5781 7.4943

Numerical Example 4

The zoom lens system of Numerical Example 4 corresponds to Embodiment 4shown in FIG. 13. Table 13 shows the surface data of the zoom lenssystem of Numerical Example 4. Table 14 shows the aspherical data. Table15 shows various data in an infinity in-focus condition. Table 16 showsvarious data in a close-object in-focus condition.

TABLE 13 (Surface data) Surface number r d nd vd Object surface ∞  117.31260 0.65000 1.91082 35.2  2 8.52610 4.80790  3* −16.48040 0.300001.58250 59.4  4* −1000.00000 0.20000  5 28.38320 1.29950 1.94595 18.0  6103.47540 Variable  7* 11.99270 2.16660 1.77200 50.0  8* −106.108901.00000  9(Diaphragm) ∞ 2.18840 10 47.78740 0.66860 1.80610 33.3 117.03670 2.82040 1.49700 81.6 12 −22.95280 1.20000 13 29.15520 1.227301.53172 48.8 14 −978.41330 Variable 15* 1297.82020 0.10000 1.85400 40.416* 12.38260 Variable 17* −47.74890 1.53130 1.54000 56.0 18* −32.605000.20000 19 29.99990 2.79110 1.74950 35.0 20 −1000.00000 (BF) Imagesurface ∞

TABLE 14 (Aspherical data) Surface No. 3 K = 0.00000E+00, A4 =1.03560E−04, A6 = −1.39133E−06, A8 = −2.73856E−07 A10 = 1.12760E−08, A12= −1.90687E−10, A14 = 1.28187E−12 Surface No. 4 K = 0.00000E+00, A4 =3.22844E−05, A6 = −9.15327E−07, A8 = −2.93196E−07 A10 = 1.12677E−08, A12= −1.69835E−10, A14 = 9.65596E−13 Surface No. 7 K = 0.00000E+00, A4 =−5.82691E−05, A6 = 1.70467E−06, A8 = −7.80465E−08 A10 = 6.18181E−10, A12= 0.00000E+00, A14 = 0.00000E+00 Surface No. 8 K = 0.00000E+00, A4 =4.26627E−05, A6 = 1.17407E−06, A8 = −6.81667E−08 A10 = 5.47668E−10, A12= 0.00000E+00, A14 = 0.00000E+00 Surface No. 15 K = 0.00000E+00, A4 =1.00000E−04, A6 = −8.01334E−06, A8 = 1.49083E−07 A10 = 2.08059E−11, A12= 0.00000E+00, A14 = 0.00000E+00 Surface No. 16 K = 0.00000E+00, A4 =1.30958E−04, A6 = −7.85025E−06, A8 = 7.72320E−08 A10 = 1.16418E−09, A12= 0.00000E+00, A14 = 0.00000E+00 Surface No. 17 K = 0.00000E+00, A4 =1.10594E−04, A6 = −5.89232E−07, A8 = −5.31506E−09 A10 = 5.30193E−10, A12= −1.60550E−11, A14 = 1.12977E−13 Surface No. 18 K = 0.00000E+00, A4 =4.43715E−05, A6 = 8.72087E−07, A8 = −6.01224E−08 A10 = 1.54512E−09, A12= −2.22912E−11, A14 = 1.10694E−13

TABLE 15 (Various data in an infinity in-focus condition) Zooming ratio2.79716 Wide-angle Middle Telephoto limit position limit Focal length14.4900 24.2343 40.5307 F-number 3.64010 5.61665 5.82481 View angle41.0303 24.5236 14.8845 Image height 10.8150 10.8150 10.8150 Overalllength 61.5694 56.7508 59.4271 of lens system BF 14.1990 14.1990 14.1990d6 16.7159 6.6005 0.6000 d14 2.0240 6.3838 13.2286 d16 5.4788 6.41628.2486 Zoom lens unit data Lens Initial Focal unit surface No. length 11 −15.44061 2 7 13.35593 3 15 −14.63973 4 17 31.85061

TABLE 16 (Various data in a close-object in-focus condition) Wide-angleMiddle Telephoto limit position limit Object distance 300.0000 300.0000300.0000 BF 14.1990 14.1990 14.1990 d6 16.7159 6.6005 0.6000 d14 2.24927.0014 14.8861 d16 5.2536 5.7986 6.5911

Numerical Example 5

The zoom lens system of Numerical Example 5 corresponds to Embodiment 5shown in FIG. 17. Table 17 shows the surface data of the zoom lenssystem of Numerical Example 5. Table 18 shows the aspherical data. Table19 shows various data in an infinity in-focus condition. Table 20 showsvarious data in a close-object in-focus condition.

TABLE 17 (Surface data) Surface number r d nd vd Object surface ∞  121.09810 0.80000 1.91082 35.2  2 9.82720 5.76180  3* −23.49740 0.450001.58700 59.6  4* −1000.00000 0.20000  5 29.71130 1.45130 1.94595 18.0  685.28620 Variable  7* 12.42550 2.05680 1.77200 50.0  8* −235.647901.00000  9(Diaphragm) ∞ 2.22850 10 38.92740 1.28120 1.80610 33.3 116.94310 2.56910 1.49700 81.6 12 −30.55640 1.50000 13 48.32620 1.245601.53172 48.8 14 −147.49250 Variable 15* −92.51690 0.30000 1.81000 41.016* 14.21170 Variable 17* 32.88590 3.38660 1.81000 41.0 18* −82.43540(BF) Image surface ∞

TABLE 18 (Aspherical data) Surface No. 3 K = 0.00000E+00, A4 =7.33157E−05, A6 = −2.79073E−06, A8 = 3.72462E−08 A10 = −3.06047E−10, A12= 0.00000E+00, A14 = 0.00000E+00 Surface No. 4 K = 0.00000E+00, A4 =3.22844E−05, A6 = −2.74529E−06, A8 = 3.20863E−08 A10 = −2.45826E−10, A12= 0.00000E+00, A14 = 0.00000E+00 Surface No. 7 K = 0.00000E+00, A4 =−3.59794E−05, A6 = 1.15750E−06, A8 = −5.04598E−08 A10 = 6.27816E−10, A12= 0.00000E+00, A14 = 0.00000E+00 Surface No. 8 K = 0.00000E+00, A4 =3.61308E−05, A6 = 8.56856E−07, A8 = −4.45020E−08 A10 = 5.94417E−10, A12= 0.00000E+00, A14 = 0.00000E+00 Surface No. 15 K = 0.00000E+00, A4 =1.00000E−04, A6 = −7.28190E−06, A8 = 1.48610E−07 A10 = 6.18095E−10, A12= 0.00000E+00, A14 = 0.00000E+00 Surface No. 16 K = 0.00000E+00, A4 =1.01967E−04, A6 = −6.31513E−06, A8 = 8.61795E−08 A10 = 1.00261E−09, A12= 0.00000E+00, A14 = 0.00000E+00 Surface No. 17 K = 0.00000E+00, A4 =−5.84835E−05, A6 = 1.04307E−06, A8 = −1.21759E−08 A10 = 1.33404E−10, A12= −1.39644E−12, A14 = 4.67445E−15 Surface No. 18 K = 0.00000E+00, A4 =−6.36928E−05, A6 = 5.52209E−07, A8 = −2.99700E−09 A10 = 6.75449E−11, A12= −1.18530E−12, A14 = 4.26784E−15

TABLE 19 (Various data in an infinity in-focus condition) Zooming ratio2.79709 Wide-angle Middle Telephoto limit position limit Focal length14.4901 24.2340 40.5300 F-number 3.64067 5.61713 5.82427 View angle40.3603 24.4537 14.8778 Image height 10.8150 10.8150 10.8150 Overalllength 67.5690 59.5636 60.8321 of lens system BF 14.1990 14.1990 14.1990d6 21.4201 8.2560 0.6000 d14 2.0147 6.2365 12.6188 d16 5.7042 6.64129.1835 Zoom lens unit data Lens Initial Focal unit surface No. length 11 −19.25728 2 7 14.96461 3 15 −15.18997 4 17 29.40870

TABLE 20 (Various data in a close-object in-focus condition) Wide-angleMiddle Telephoto limit position limit Object distance 300.0000 300.0000300.0000 BF 14.1990 14.1990 14.1990 d6 21.4201 8.2560 0.6000 d14 2.27266.9486 14.4974 d16 5.4463 5.9290 7.3049

The following Table 21 shows the corresponding values to the individualconditions in the zoom lens systems of each of Numerical Examples.

TABLE 21 (Values corresponding to conditions) Numerical ExampleCondition 1 2 3 4 5 (1) |f₃/f_(W)| 1.07 1.37 1.08 1.01 1.05 (2) d₃/f_(W)0.03 0.04 0.03 0.01 0.02 (3) d₁/f_(W) 0.54 0.43 0.56 0.50 0.60

The zoom lens system according to the present invention is applicable toa digital still camera, a digital video camera, a camera for a mobiletelephone, a camera for a PDA (Personal Digital Assistance), asurveillance camera in a surveillance system, a Web camera, avehicle-mounted camera or the like. In particular, the zoom lens systemaccording to the present invention is suitable for a photographingoptical system where high image quality is required like in a digitalstill camera system or a digital video camera system.

Also, the zoom lens system according to the present invention isapplicable to, among the interchangeable lens apparatuses according tothe present invention, an interchangeable lens apparatus havingmotorized zoom function, i.e., activating function for the zoom lenssystem by a motor, with which a digital video camera system is provided.

Although the present invention has been fully described by way ofexample with reference to the accompanying drawings, it is to beunderstood that various changes and modifications will be apparent tothose skilled in the art. Therefore, unless otherwise such changes andmodification depart from the scope of the present invention, they shouldbe construed as being included therein.

What is claimed is:
 1. A zoom lens system, in order from an object sideto an image side, comprising a first lens unit having negative opticalpower, a second lens unit having positive optical power, a third lensunit having negative optical power, and a fourth lens unit havingpositive optical power, wherein the third lens unit moves along anoptical axis in focusing from an infinity in-focus condition to aclose-object in-focus condition, and the following conditions (1) and(2) are satisfied:0.5<|f ₃ /f _(W)|<2.0  (1)0.005<d ₃ /f _(W)<0.070  (2) where f₃ is a focal length of the thirdlens unit, d₃ is an optical axial thickness of the third lens unit, andf_(W) is a focal length of the entire system at a wide-angle limit. 2.The zoom lens system as claimed in claim 1, wherein the followingcondition (3) is satisfied:0.30<d ₁ /f _(W)<0.85  (3) where d₁ is an optical axial thickness of thefirst lens unit, and f_(W) is a focal length of the entire system at awide-angle limit.
 3. The zoom lens system as claimed in claim 1, whereinthe fourth lens unit is fixed relative to an image surface in zoomingfrom a wide-angle limit to a telephoto limit at the time of imagetaking.
 4. The zoom lens system as claimed in claim 1, wherein the firstlens unit moves along the optical axis in zooming from a wide-anglelimit to a telephoto limit at the time of image taking.
 5. Aninterchangeable lens apparatus comprising: a zoom lens system as claimedin claim 1; and a lens mount section which is connectable to a camerabody including an image sensor for receiving an optical image formed bythe zoom lens system and converting the optical image into an electricimage signal.
 6. A camera system comprising: an interchangeable lensapparatus including a zoom lens system as claimed in claim 1; and acamera body which is detachably connected to the interchangeable lensapparatus via a camera mount section, and includes an image sensor forreceiving an optical image formed by the zoom lens system and convertingthe optical image into an electric image signal.